Tomcat i7221 S5150
Chapter 3: BIOS Setup
3-13
http://www.tyan.com
DRAM Timing Selectable
This option permits you to either manually select memory timings, or allow the SPD (Serial
Presence Detect) to determine the said timings automatically.
Manual /
By SPD
Note
On all memory timing settings, lower number is more aggressive.
CAS Latency Time
This setting controls the time delay (in clock cycles - CLKs) that passes before the DRAM
starts to carry out a read command after receiving it. This also determines the number of CLKs
for the completion of the first part of a burst transfer. In other words, the lower the latency, the
faster the transaction.
Auto
/ 2 / 2.5 / 3
DRAM RAS# to CAS# Delay
This setting is the number of cycles from when a bank activate command is issued until a read
or write command is accepted, that is, before the CAS becomes active.
Auto
/ 5 / 4 / 3 /2
DRAM RAS# Precharge
This setting is the number of cycles needed to return data to its original location to close the
bank or number of cycles to page memory before the next bank activate command can be
issued.
Auto
/ 5 / 4 / 3 / 2
Precharge Delay <tRAS>
This timing controls the length of the delay between the activation and precharge commands --
basically how long after activation can the access cycle be started again. This influences row
activation time that is taken into account when memory has hit the last column in a specific
row, or when an entirely different memory location is requested.
Auto
/ 4 ~ 10
System Memory Frequency
Changing this option allows the memory to be run asynchronously from the FSB but it is best if
it is left at AUTO.
Auto
/ 400 / 533
System BIOS Cacheable
Enabling this option will cause the BIOS code from ROM to be copied on to the much faster
RAM at location F0000h-FFFFFh, thus increasing system performance. However, if any
program writes to this memory area, a system error may result.
Disabled /
Enabled
Video BIOS Cacheable
Enabling this option will cause the VIDEO BIOS code from the video adapter’s ROM to be
copied on to the much faster RAM, thus increasing system performance. However, if any
program writes to this memory area, a system error may result.
Disabled
/ Enabled
Memory Hole at 15M-16M
Certain ISA cards require exclusive access to the 1MB block of memory, from the 15th to the
16th megabyte, to work properly. This BIOS feature allows you to reserve that 1MB block of
memory for such cards to use.
